The present invention relates generally to coextruded multilayer film materials and more particularly to containers made from the multilayer film materials.
Containers used for the shipping, storing, and delivery of liquids, such as medical or therapeutic fluids, are often fabricated from single-ply or multi-ply polymeric materials. Two sheets of these materials are placed in overlapping relationship and the overlapping sheets are bonded at the inner surfaces of their outer peripheries to define a chamber or pouch for containing liquids. It is also possible to extrude these materials as a tube and to seal longitudinally spaced portions of the tube to define chambers between two adjacent seals. Typically, the materials are joined along their inner surfaces using bonding techniques such as heat sealing, radio-frequency sealing, thermal transfer welding, adhesive sealing, solvent bonding, sonic sealing, and laser welding.
For most applications, the seal formed must be of sufficient strength to withstand the stresses generated by transporting, dropping, or agitating the liquid-filled container. Problems have been encountered with certain materials that do not bond well with themselves or other materials. Problems have also been encountered in forming strong seals in containers having sidewalls made of a layered material. If seals of sufficient strength cannot be formed, this alone could prevent the container from ever reaching the marketplace.
Thus, to achieve a reliable, consistent seal of sufficient strength using any of the above-mentioned bonding techniques, the sealing faces of the film materials must be compatible. In the case of multilayered film materials formed by coextrusion, it also requires that the coextruded film have a high degree of resistance to delamination between the layers, i.e., that each layer be compatible with every layer it contacts. The compatibility requirement places a practical limitation on the products that can be manufactured and, therefore, limits design options. The compatibility requirement also presents problems in attaching other features to the film materials such as when attaching access ports, tail seals or tail hangers to containers constructed from the multilayer films.
There are many applications, however, where using incompatible materials would be desirable if the materials could be reliably bonded into a container in a cost effective manufacturing operation. For instance, applications utilizing coextruded multilayered films have the need for such a material structure. A flexible container could then be manufactured from multilayered films wherein the outer layers of the films allow for bonding strong peripheral seams while the inner layers of the films provide for specific functionalities, such as cell culture surfaces and inert surfaces to certain pharmacological agents.
Problems have been encountered in sealing containers wherein the container walls are multilayered and wherein the inner layers are made from polystyrene. The bond formed between the polystyrene layers is not sufficiently strong to withstand the hydraulic shock generated by container fluids. In one such example, a cell culture container described in co-pending and commonly assigned U.S. patent application Ser. No. 08/330,717, now U.S. Pat. No. 6,297,046, is constructed of a multilayered material having an outer layer of a polymer blend of styrene-ethylene-butene-styrene (xe2x80x9cSEBSxe2x80x9d) block copolymer (40%-85% by weight), ethylene vinyl acetate (0-40% by weight), and polypropylene (10%-40% by weight) and an inner layer of a polystyrene. It was found that only weak seams could be achieved by sealing or bonding the polystyrene layers to one another. The seams were considered xe2x80x9cfragile,xe2x80x9d and the container was not sufficiently robust enough to tolerate normal handling procedures. Also, the resulting filled cell culture container was not capable in many instances of being dropped at heights above six feet without seal failure.
Copending and commonly assigned U.S. patent application Ser. No. 08/998,256, now U.S. Pat. No. 6,083,584, discloses an improved seal construction for the cell culture container by encapsulating the peripheral margins of the film materials as opposed to joining the inner facing surfaces of the films as conventional methods do. By bonding the peripheral margins through encapsulation, the container can withstand elevated mechanical stresses. Encapsulation, however, can be a time-consuming and intricate procedure, especially when it is necessary to encapsulate three or four sides of a container.
Due to the problems relative to sealing containers manufactured from multilayered materials, there is a need for creating a multilayered material that is capable of forming a suitably strong peripheral seal when the multilayered film is formed into a container.
The present invention relates to multilayered films and containers made from the films.
In a first aspect of the present invention, a multilayered film suitable for medical uses is provided that is coextruded in a machine direction. The film has a first layer defining a pair of peripheral edges extending in a direction parallel to the machine direction. The film also has a second layer adhered to the first layer, wherein the second layer is positioned within the peripheral edges to define a stripe.
According to another aspect of the invention, the film has a width and a thickness wherein the thickness of the film is substantially uniform across the width of the film.
According to a further aspect of the invention, the first layer of the film is composed of a polyolefin, and the second layer of the film is composed of a polystyrene.
According to yet another aspect of the invention, the first layer of the film has a first flange and a second flange. The flanges extend in a lateral direction wherein the second layer is positioned between the flanges. The first layer also has a channel positioned between the flanges and extending parallel to the flanges wherein the second layer is positioned in the channel. The thickness of the film is substantially uniform across the width of the film.
According to a further aspect of the invention, the second layer is positioned in the channel and defines an overlap area. The second layer has a thickness of 0.0003 in. to 0.003 in. The first layer has a thickness of 0.006 in. to 0.012 in. at the flanges and a thickness of 0.0057 in. to 0.009 in. at the overlap area.
According to another aspect of the invention, the second layer of the film defines an inner cell growth surface.
According to a further aspect of the invention, when the film is viewed from a direction perpendicular to the machine direction, the film is noncontinuous by having a first layer section adjacent the stripe of the second layer adjacent another first layer section.
According to yet a further aspect of the invention, the second layer has a first longitudinal portion removed to defme a first longitudinal segment on the first layer, and the second layer has a second longitudinal portion removed to define a second longitudinal segment on the first layer.
According to another aspect of the invention, a container suitable for medical uses is constructed from the film.
Other advantages and aspects of the present invention will become apparent upon reading the following description of the drawings and detailed description of the invention.